Romney has opened up a comfortable lead over Santorum in national polls, and is poised to rack up another primary victory Tuesday in Wisconsin.

Santorum hasn’t given any indication he’s contemplating dropping out, and downplayed the delegate race on Friday at a campaign event.

"Ladies and gentlemen, we need a contrast. Not a contest between Tweedledum and Tweedledee," Santorum said in Wisconsin. "Folks, we're not gonna win an election on math. We're gonna win the election on vision."

But vision might not be enough to keep Santorum’s campaign alive, particularly if the tide turns against him in his home state of Pennsylvania, which holds its GOP primary on April 24.

Polls give Santorum a commanding lead in Pennsylvania, but he has seen similar leads vanish overnight under a barrage of attack ads from Restore Our Future, a super-PAC that supports Romney.

Santorum appears confident that he’ll win his home-state primary, and recently touted polls that show him with a double-digit lead there.

But GOP consultants said Santorum needs to be devising a strategy for leaving the race, and might want to save himself the embarrassment of potentially losing on his home turf next month.

"The race is absolutely over," said GOP strategist Patrick Griffin, who consulted for both President George H.W. Bush and President George W. Bush. "The jig is up here, it's just a question of when Butch and Sundance decide to put up the white flag."

Griffin said Santorum would be at a major risk of losing Pennsylvania once Romney starts to focus his time and resources there. What Santorum should be doing, Griffin said, is planning a graceful exit.

"The thing to do is to get through Wisconsin and step up and say, 'OK, we fought the good fight, we did the good thing, we had a good message that appealed again and again to a small constituency of the party," Griffin said.

Santorum's strong showing in 2012 has elevated him into the national ranks of the Republican Party, Griffin said, but he risks losing that prominence by staying in the race too long.

"You don't want to hang in there so long that you become 'Ron Paul-irrelevant,' " Griffin said, referring to the Texas congressman who is also running for president.

Griffin said that if Santorum dropped out at the right time, he could still earn a spot in a Romney administration, presuming he beats President Obama in November.

Romney might not see things the same way. In a recent appearance on “The Tonight Show,” host Jay Leno asked Romney what job Santorum would have in his administration. “Press secretary,” Romney joked, in reference to Santorum’s recent run-in with a New York Times reporter.

Strategist Chris Bravacos, a prominent Pennsylvania Republican strategist, said that the longer Santorum stays in the race, the more he risks damaging his political future.

"I think what's undermining him now is it's much harder for folks to believe that this is a fight worth making any longer," Bravacos said. "It's pretty obvious that Romney's going to be the nominee."

Bravacos said Santorum will likely have more trouble in Pennsylvania than one might think. To Pennsylvanians he served as senator, Santorum is an establishment politician, rather than an outsider trying to shake up his party.

"When he gets to Pennsylvania, he has endorsements of a lot of the state Senate. His TV is the governor's TV guy," Bravacos said. "His campaign manager for the state was the governor's campaign manager."

Bravacos said Santorum "can't really" make the outsider politician claim in Pennsylvania that he's made elsewhere in the country.